The filing is full of revelations about Courtney's contact with the FBI this week, including his alleged confession. It comes in advance of a hearing Monday, where a judge is to decide whether Courtney should remain jailed without bond.

"The defendant stated that he diluted the strength of the chemotherapy drugs out of greed and in order to make more money," the court papers said.

Courtney, 48, was charged Tuesday with a single federal charge of misbranding and adulteration of a drug. His attorney, Jean Paul Bradshaw, has said Courtney will plead innocent. Bradshaw did not immediately return calls by The Associated Press seeking reaction to Friday's filing.

The FBI says samples tested after being prepared by Courtney's Research Medical Tower Pharmacy contained between 39 percent and less than 1 percent of the expensive drugs.

Courtney also admitted diluting the chemotherapy drugs Paraplatin and Platinol, according to the filing. Authorities believe the same people got all four diluted drugs, meaning the new revelation about Paraplatin and Platinol wouldn't affect a new group of patients.

Federal agents first interviewed Courtney on Monday, the same day they searched his Research Medical Tower Pharmacy. Courtney told them he didn't know how the mixture of drugs and saline in intravenous drug bags he had prepared could have been so weak.

Then he was charged. On Wednesday, Courtney turned himself in, and in his attorney's presence began telling a different story to federal investigators, according to the filing.

"During this interview the defendant admitted that the allegations in the pending complaint are true," the filing stated. "The defendant admitted that beginning in November of 2000, and intensifying in March through May of 2001, he knowingly reduced the potency/strength/concentration of Gemzar and Taxol in IV drug bags ordered by one specific physician."

The filing stated Courtney said the dilutions were limited to between 30 and 35 patients of one physician. Prosecutors, however, said they were trying to determine the accuracy of that, and officials have repeatedly said hundreds of patients could be affected.

Courtney told the federal agents that beginning in November he provided Gemzar and Taxol mixtures at about half the strength requested by doctors, then reduced that to 30 to 40 percent. Testing requested by a doctor and investigators found one sample with less than one percent of the drug requested. Courtney told investigators he had meant to mix that treatment at 30 to 40 percent, too.

Courtney also claimed he acted alone without the help of the other physicians who worked for him or the doctor who ordered the chemotherapy treatments.

The FBI has said homicide or manslaughter charges are possible if investigators link the diluted drugs to a death, though no such link has been made. Federal authorities have said they expect to call a grand jury to consider indicting Courtney.

A government hot line for people who think they might be affected had logged more than 500 calls by Thursday night.

The allegations have prompted doctors who used Courtney's chemotherapy mixes to scour their records to find patients who got the treatments.

The drugs were distributed directly to doctors by Courtney's pharmacy in Kansas City, and authorities say there's no reason to worry about Gemzar and Taxol handled by other pharmacies.

The alleged dilution was first noticed by a sales representative for Gemzar maker Eli Lilly and Co., who found a discrepancy between the amount of Gemzar the pharmacy ordered and the amount it billed a doctor later identified as Verda Hunter. Tests ordered by Hunter and federal authorities allegedly showed greatly reduced concentrations of the drugs.

According to the charge against Courtney, Hunter "made several unsuccessful attempts to directly contact the Eli Lilly Corporation," then sent the company a letter on May 27. She never got a response, according to the complaint.

On Friday, Lilly spokesman Jeffrey Newton said it's not the company's job to monitor its products once they're delivered to pharmacists.

"It's not an appropriate expectation of our industry to be responsible for every pharmacy. That's not what our company does," Newton said.

Federal authorities believe Courtney has over $10 million in assets, including his two pharmacies. Those could be seized by the government if the government convicts Courtney and ties the assets to the allegations. And at least two private lawsuits have been filed, one of them seeking class-action status.